The present invention relates to a piezoelectric element formation member in which piezoelectric elements deformed when a piezoelectric material layer is applied with a voltage are integrally formed; a piezoelectric element formation unit; a piezoelectric actuator unit; and a liquid injection head incorporating such a piezoelectric element formation member. In particular, the present invention relates to an ink jet recording head in which ink supplied to a pressure generating chamber being communicated with a nozzle orifice is pressurized by a piezoelectric element to allow the nozzle orifice to eject ink droplets.
As an ink jet recording head wherein a pressure generating chamber being communicated with a nozzle orifice for ejecting ink droplets is partially constructed by a vibration plate to allow this vibration plate to be deformed by a piezoelectric element so that ink in the pressure generating chamber is pressurized to eject ink droplets from the nozzle orifice. It is well known an ink jet recording head using a piezoelectric actuator of a longitudinal vibration mode which expands or contracts in the axial direction of the piezoelectric element.
For example, Japanese Patent Publication No. 2001-277525A (cf., FIGS. 2 and 3, pages 8–10) discloses Such a piezoelectric actuator unit comprising an actuator array in which a plurality of lamination type piezoelectric elements are arrayed and a fixation plate on which the actuator array is mounted. The actuator array is formed by alternately laminating a internal common electrode and an internal individual electrode while sandwiching a piezoelectric body therebetween. This actuator array has an external individual electrode and a external common electrode on surfaces thereof. The external individual electrode is connected to an internal individual electrode exposed to the distal end face of the actuator array. On the other hand, the external common electrode is connected to a internal common electrode exposed to a proximal end face of the actuator array. A contact is formed on each external individual electrode and each external common electrode. Connection terminals of a flexible cable is mounted on the contacts by soldering or the like.
However, in a piezoelectric actuator unit having such a structure, the external individual electrode and the external common electrode provided on the surface of each piezoelectric element are separated in a longitudinal direction thereof. Thus, the contact of the external individual electrode and the contact of the external common electrode, onto which the connection terminals of the flexible cable are mounted, are placed at different positions in the longitudinal direction of the piezoelectric element. In an actual case, the contacts of the external electrodes and the connection terminals of the flexible cable are isolated by providing an insulating layer such as a resist. Since it is difficult to accurately control the thickness of such an insulating layer, a defective connection would be occurred between the contacts and the connection terminals due to the error in the thickness of the insulating layer.
Besides, Japanese Patent Publication No. 2000-94677A (cf., FIGS. 1 to 4 and pages 3–4) discloses a structure in which slits are formed, by a wire saw, in a piezoelectric diaphragm formed with a conductive layer on a surface thereof, thereby dividing the conductive layer to form external individual electrodes and external common electrodes.
According to this structure, the flexible cable can be connected in a relatively favorable manner, but the manufacturing efficiency is low. That is, since the inspection for the connection failure between the external individual electrode and the external common electrode must be performed after the formation of the slits, not only the manufacturing efficiency is low but also the yield is low. This type of problem is also caused not only in an ink jet recording head for electing ink but also in a liquid injection head for ejecting liquid other than ink.